The field of this invention generally related to chemical production methods employing electro-catalytic reaction mechanisms, and more particularly, to methods and systems using vegetable oil and other non-petroleum oil feedstocks to make biodiesel, acetic acid, glycerol, select fatty acids and polymers, and the like.
Chemical syntheses are ubiquitous and important to numerous industries throughout the world, particularly the industries involved in the production of organic chemicals, polymers, pharmaceuticals, inorganic chemicals, and specialty chemicals. Due to the time and cost of various chemical synthesis processes, industries are always striving to improve current devices and methods for chemical synthesis; including for example, ways to reduce the time and cost of purification/separation steps involved, methods to decrease the energy cost of production, methods to increase overall product yields, and improvements in the efficiency of chemical synthesis.
Biodiesel
Fossil fuels, particularly coal, oil, and natural gas, are the primary fuels of industrialized society. However, the supply of fossil fuel is limited and non-renewable, and its use is believed to contribute to substantial environmental pollution and health issues. Based on some recent estimates of consumption rate, the U.S. will deplete its natural reserve of all fossil fuels by 2036, and by the year 2041, the entire planet will deplete its natural reserve of all fossil fuels if this same rate of consumption continues to grow. Furthermore, roughly 22 gigatons of carbon dioxide (CO2) presently are being released into the atmosphere each year from use of fossil fuels, and more than 1.5 million tons of sulfur dioxide pollution are produced in the U.S. each year by vehicle engines burning fossil fuel. Because, the natural environment cannot rapidly reuse the CO2, the amount of CO2 in the atmosphere continues to increase. Thus, there is a tremendous resource and environmental burden to find alternative renewable energy sources to the non-renewable fossil fuel.
A viable alternative to fossil fuel is biodiesel, a renewable source of energy. Biodiesel (or bio-fuel) is the name for a variety of ester-based fuels (e.g., fatty esters) generally made from vegetable oils, such as soybean oil, canola or hemp oil, or sometimes from animal fats through a simple transesterification process. This renewable source is as efficient as petroleum diesel in powering unmodified diesel engine. Since the introduction of biodiesel fuel in South Africa prior to World War II, work has proceeded to increase its viability as a fuel substitute. Recent environmental and economic pressures have hastened the need to enhanced development of this renewable energy source.
Biodiesel offers many advantages. Biodiesel runs in any conventional, unmodified diesel engine; thus, no engine modifications are necessary. Biodiesel can be used alone or mixed in any amount with petroleum diesel fuel. For example, a 20% blend of biodiesel with (petroleum-based) diesel fuel is called “B20,” a 5% blend is called “B5,” and so on. This renewable fuel can be stored anywhere that petroleum diesel fuel is stored and all diesel fueling infrastructure including pumps, tanks and transport trucks can use biodiesel without modifications. In addition to the compatibility with diesel-based infrastructures, biodiesel can provide a net reduction in CO2 emissions, and biodiesel produces no sulfur dioxide when burned. Furthermore, biodiesel is considered biodegradable and non-toxic.
Conventional biodiesel improves engine emissions in most categories when compared to pipeline petroleum diesel fuel. Blends containing higher concentrations of conventional biodiesel, however, disadvantageously show a proportional increase in emissions of nitrogen oxides (NOX). For instance, it is well documented that use of a conventional biodiesel blended with petroleum diesel fuel in a 80% petroleum/20% biodiesel blend results in increased nitrous oxide emissions by 2 to 11%. Presently, NOX emissions are a significant limitation to the widespread adoption of biodiesel fuels.
Some researchers have sought to address the NOX issue by the addition of certain fuel additives to the biodiesel. For example, U.S. Pat. No. 5,578,090 to Bradin discloses a fuel additive composition including fatty acid alkyl esters and glyceryl ethers. The additive-containing fuel is made by a multi-step process that includes separation of glycerol from biodiesel, conversion of glycerol to glycerol ether, and then addition of the glycerol ether back into the biodiesel fuel. Other researchers describe controlling engine emission NOX by adding water to the fuel, which cools the combustion process and reduces the formation of NOX. However, that process undesirably lowers fuel BTU value by replacing fuel with water. It would be desirable to provide a biodiesel fuel that would lower NOX emissions without lowering fuel BTU value, and to provide simpler and less expensive methods producing such fuels.
Conventional methods of producing biodiesel fuel or fuel additive use existing technologies that relate to surfactant manufacturing processes. These are widely known and practiced through out the industry. Traditionally, biodiesel is synthesized via transesterification, as exemplified in FIG. 1. Transesterification, in relation to biodiesel, involves taking a triglyceride molecule or a complex fatty acid, neutralizing the free fatty acids, removing the glycerin, and creating an alcohol ester. This is accomplished by mixing a wood alcohol, e.g., methanol, with sodium hydroxide to make sodium methoxide. This dangerous liquid is then mixed into vegetable oil. As the reaction proceeds, contaminant formation of glycerol and possibly some surfactant occurs. The entire mixture then settles, with glycerin on the bottom and methyl esters, or biodiesel, on top (supernatant). Expensive separation of these contaminants is required to produce pure methyl ester or biodiesel.
This typical industry process method includes the use of catalytic reactions with high temperature and pressure. The combined utilization of these factors is to excite electrons to migrate back and forth across the surface of the catalysis to drive the reaction process to completion. Process challenges include issues of improving the decontamination processes for regenerating the catalysis, reducing dependency on homogenous catalysis that produce unwanted species during the reaction, developing continuous large volume processes to help reduce costs, reducing environmental impact of decontamination processes, constructing better heterogeneous catalysis without dependency on rare earth materials, constructing a catalysis to work more efficiently with heavier crude oils, improving pharmaceutical process purity with better catalytic reactions, lower temperature and pressure requirements of catalytic reactions, improving surface pour area of catalysis to accept larger molecules, reducing contamination reactions inside the catalysis during production operations, researching to find catalysis that perform reactions in a shorter time period, and improving molecular bonding during catalytic reactions.
After the reaction, the unreacted methanol, or ethanol, and the catalyst must be removed to purify the methyl ester. The necessity of this further processing is the crux of the problem with conventionally produced biodiesel fuels: They are not cost competitive with petroleum diesel fuel in part due to the process expense. In fact, most biodiesel fuels are more than 1.5 times higher in production cost than petroleum derived diesel. Thus, there is a need in the industry for devices and methods which reduce the use of catalysts and increase useable byproducts, such as hydrogen gas in the production of biodiesel.
Another problem of conventional biodiesel fuel is the cost of refined oil. Crude vegetable oil has considerable free fats that react with the catalysis to form fuel contaminants, such as surfactant and glycerol. Therefore, crude vegetable oil is not a suitable oil source for conventional biodiesel production. These contaminants are costly to remove and formation must be avoided or reduced whenever possible. Conventional biodiesel production requires a homogenous catalysis that produces unwanted side reactions; however, such side reactions preferably should be minimized or eliminated from the process.
Reaction time for conventional batch processes of making biodiesel typically ranges from 1 to 8 hours, and separation time for contaminant removal adds 8 to 16 hours. Thus, a gallon of biodiesel requires about 24 hours of processing time. Some researches have attempted to alleviate the problem of the slow reaction rate. Examples include the use of non-reactive co-solvents, which converts the two-phase system into a single-phase system. For instance, Canadian Patent Application No. 2,131,654 discloses using simple ethers, such as tetrahydrofuran (THF) and methyltertiarybutylether (MTBE) as co-solvents. Molar ratios of alcohol to triglyceride of at least 4.5:1 and more preferably at least about 6:1 are disclosed, with typical ratios being in the range of 6:1 to 8:1. The reaction is further discussed by D. G. B. Boocock et al in Biomass & Bioenergy, 11(1): 43-50 (1996). However, this process still produced numerous byproducts which require expensive and time-consuming purification techniques. For these reasons, conventional processes are not economically competitive with petroleum diesel.
Various esterification processes are described in the art. Examples include U.S. Pat. No. 4,164,506 to Kawahara et al. (disclosing (a) esterification of free fatty acids in the presence of an acid catalyst, (b) allowing the product mixture to separate into a fat layer and an alcohol layer so as to obtain a refined fat layer, and (c) then subjecting the fat layer to transesterification with a base catalyst); U.S. Pat. No. 4,695,411 to Stern et al. (disclosing a multi-step reaction involving acid transesterification with alcohol in the presence of 1-60% water and separating a resulting glycerol phase, reducing the free acidity of the remaining ester phase and then transesterification in the presence of a base catalyst); U.S. Pat. No. 4,698,186 to Jeromin et al. (disclosing a process for reducing the free acid content of fats and oils by esterification with an alcohol in the presence of an acidic cation exchange resin); U.S. Pat. No. 5,525,126 to Basu et al. (disclosing esterification of mixtures of fats and oils by using a calcium acetate/barium acetate catalyst, with undesirable process conditions of 200° C., 500 psi, and a reaction time of three hours); U.S. Pat. No. 5,713,965 to Foglia et al. (disclosing use of lipases to transesterify mixtures of triglycerides and free fatty acids, with reactions requiring 4 to 16 hours to reach conversion rates of 95%); and U.S. Pat. No. 5,520,708 to Johnson et al. (disclosing reaction of triglycerides with methanol in the presence of base to produce fatty acid methyl esters). Various carboxylation processes also are known. Examples include U.S. Pat. No. 5,476,971 to Gupta (disclosing reacting pure glycerol with isobutylene in the presence of an acid catalyst in a two phase reaction to produce mono-, di- and tri-tertiary butyl ethers of glycerol); U.S. Pat. No. 4,013,524 to Tyssee (disclosing method of electrolytic carboxylation and dimerization of olefinic nitrites, esters and amides); and U.S. Pat. No. 4,028,201 to Tyssee (disclosing a procedure for electrolytic monocarboxylation of olefinic nitriles, esters and amides in which the reaction is moderated by protons to direct it toward monocarboxylation); U.S. Pat. No. 5,225,581 to Pintauro (disclosing electrocatalytic process for hydrogenating an unsaturated fatty acid, triglyceride, or mixtures thereof as an oil or fat); U.S. Pat. No. 5,891,203 to Ball et al. (disclosing use of blends of diethanolamine derivatives and biodiesel as an additive for improving lubricity in low sulfur fuels and to fuels and additive concentrates comprising said lubricity additives.)
Examples of other fuel production methods are disclosed in U.S. Pat. No. 6,440,057 to Ergun et al., which discloses a method for producing fatty acid methyl ester, including compounding saturated and unsaturated higher fatty substances from at least one of vegetable and animal with an alkaline solution dissolved in alcohol to form a mixture, and in U.S. Pat. No. 6,248,230 to Min et al., which discloses a method for manufacturing cleaner fuels, in which NPC (Natural Polar Compounds), naturally existing in small quantities within various petrolic hydrocarbon fractions, are removed from the petrolic hydrocarbon. U.S. Pat. No. 6,086,645 to Quiqley discloses low sulfur fuel compositions, which exhibit improved lubricity compared to the low sulfur fuels alone.
Thus, there is a need for developing devices and methods to improve chemical reaction performance, particularly with respect to the production of biodiesel, while lowering production costs and yielding higher quality products. These improvements include efficiency improvements in conversion reactions, as well as final product purity, energy savings, and lowering production costs of biodiesel.
Polymerization
There also exists a need for improved devices and methods for efficient synthesis of polymers. Currently, many polymerization techniques in the art result in multiple reactions which require tedious separation and/or purification steps. Reducing the reaction steps such as purification and separation steps are invaluable to industries, saving millions of dollars in production cost and reaction time. For example, polyesters are important polymers with multiple usages; thus industries would benefit for an efficient synthesis technique. Thus, there is also a need in the industry for devices and methods for improving the efficiency and cost of production for the synthesis of polymers.
Surfactant
Another widely commercialized chemical industry relates to surfactants. A surfactant is a material that can greatly reduce the surface tension of water when used in very low concentrations. This material or molecule is made up of water soluble (hydrophilic) and water insoluble (hydrophobic) components. The hydrophobe may be for example the equivalent of an 8- to 18-carbon hydrocarbon, and can for example be aliphatic, aromatic, or a mixture of both. The synthesis of surfactant typically requires some form of catalyst, an oil or fat, and strong base such as sodium hydroxide. Similar to the syntheses described above, the current methods and devices for the production of surfactant requires several separation and/or purification steps and the use of catalysts, which can be toxic.
The sources of hydrophobes are normally natural fats and oils, petroleum fractions, relatively short synthetic polymers, or relatively high molecular weight synthetic alcohols. The hydrophilic groups give the primary classification to surfactants, and are anionic, cationic and non-ionic in nature. The anionic hydrophiles are for example carboxylates (soaps), sulphates, sulphonates and phosphates. The cationic hydrophiles may be for example some form of an amine product. The non-ionic hydrophiles associate with water at the ether oxygens of a polyethylene glycol chain. In each case, the hydrophilic end of the surfactant is strongly attracted to the water molecules and the force of attraction between the hydrophobe and water is only slight. As a result, the surfactant molecules align themselves at the surface and internally so that the hydrophile end is toward the water and the hydrophobe is squeezed away from the water.
Surfactants have wide commercial usage. Representative examples of surfactant usage include soaps, detergents, fabric softeners, shampoo, cosmetics (e.g., skin care formulations, sunscreens), environmental remediation (e.g., remediation of contaminated aquifers, soil stabilization, sludge treatment, enhanced oil/petroleum recovery and/or dispersants), mineral flotation, and medical applications (e.g., liposome drug delivery). It would be desirable to provide improved and more efficient processes and devices for surfactant synthesis.
Acetic Acid
Acetic acid (CH3COOH) is a carboxylic acid, which is used in a variety of products and processes. Acetic acid is essential in widespread industrial applications from textile to herbicide industries. In one particular process, acetic acid is used in the manufacture of acetate esters, where it is used to make materials such as cellulose acetate (used in rayon and photographic film) and polyvinyl acetate (used in latex paints and wood glues). It is an ideal solvent for many organic compounds and some inorganic compounds. Chemically, acetic acid shares most of the properties of carboxylic acids in general, including the ability to react with alcohols and amines to produce esters and amides, respectively. In addition, it can react with alkenes to produce acetate esters. When heated above 440° C., it decomposes to produce carbon dioxide and methane, or to produce ketene and water.
Acetic acid is the chemical component that gives vinegar, typically 4-8% acetic acid by volume, its sour taste. Many countries require that the acetic acid found in vinegar be produced by natural fermentation rather than by non-biological means. Vinegar is manufactured by fermenting various starchy, sugary, or alcoholic foodstuffs with Acetobacter bacteria. Commonly used feed stocks include apple cider, wine, and grain or potato mashes. The vinegar is then distilled from the fermentation broth.
Industries producing acetic acid face expensive separation and purification challenges. Most acetic acid made for industrial uses one of three chemical processes: butane oxidation, acetaldehyde oxidation, or methanol carbonylation.
When butane is heated with air in the presence of various metal ions, including those of manganese, cobalt, and chromium, peroxides form and then decompose to produce acetic acid according to the chemical equation:C4H10+2½O2→2CH3COOH+H2O  EQ. 1Typically, the reaction is conducted at temperature and pressure conditions of 150° C. and 55 atm. Several side products are formed, including butanone, ethyl acetate, formic acid, and propionic acid. These must be removed after reaction to purify the product.
Under similar conditions and using similar catalysts used for butane oxidation, acetaldehyde can be oxidized by the oxygen in air to produce acetic acidCH3CHO+½O2→CH3COOH  EQ. 2Using modern catalysts, this reaction can have an acetic acid yield greater than 95%. The major side products are ethyl acetate, formic acid, and formaldehyde, all of which have lower boiling points than acetic acid and are readily separated by distillation. Acetaldehyde oxidation is the second most widely-used method of acetic acid production, second only to methanol carbonylation.
In the methanol carbonylation reaction, methanol and carbon monoxide react to produce acetic acid according to the chemical equation:CH3OH+CO→CH3COOH  EQ. 3
Because both methanol and carbon monoxide are relatively inexpensive, methanol carbonylation long appeared to be an attractive method for acetic acid production, and patents on such processes were granted as early as the 1920's. However, the high pressures needed (200 atm or more) discouraged commercialization.
Today the principal methods of producing acetic acid industrially, with greater than 60% of the world's total acetic acid output per year, comprise improved methods of carbonylation of methanol. Over the years, improvements in catalysis have increased the selectivity of the reaction and decreased the pressure and temperature requirements of the process. For example, in 1960, BASF introduced a commercial process using a cobalt catalyst, which operates at high temperatures and pressures (250° C. and 680 bar), with a selectivity of methanol to acetic acid of about 90%. In 1966, the Monsanto Company found that using a rhodium catalyst made the reaction possible under milder conditions (180° C., 30-60 bar), with a selectivity of about 99% relative to methanol. In 1995, BP Chemicals introduced the Cativa process, which is based upon an iridium catalyst, and boasts improved catalyst stability, better reaction rates, and reduced by-product formation. In all of these processes, however, an organometallic species must be present with the reactants for the reaction to proceed.
Typically, the catalyst is a homogenous catalyst, which is evenly dispersed in a liquid phase. This homogeneously catalyzed reaction proceeds at 22 bar and 192° C., where methanol and carbon monoxide react to form acetic acid as shown by EQ. 3. However, due to the complexity of the catalytic reaction, some of the intermediates are not converted to acetic acid. The main by-products are hydrogen gas, methyl acetate, acetaldehyde, propionic acid, and methyl iodide. Hydrogen is formed in the system by the water-gas shift reaction,CO+H2O→CO2+H2  EQ. 4which combines carbon monoxide and water to form carbon dioxide and hydrogen gas. This reaction consumes a minor amount of products, and proceeds since the reactor is at a high temperature and pressure.
Methyl acetate, an intermediate, can react with water to form acetic acid. This reaction requires the presence of a catalyst and the reaction temperature and pressure to proceed. The following equation shows the reaction of the methyl acetate by-product to acetic acid when combined with water at reaction conditions.CH3COOCH3+H2O→3/2CH3COOH+H2  EQ. 5Propionic acid is the main impurity in the final product, since its chemical properties are similar to those of acetic acid. Propionic acid is generated from the carbonylation of ethanol, which can be present as an impurity in the methanol feed or from reduction of acetaldehyde by hydrogen in the system. The following equation shows the carbonylation of ethanol to form propionic acid.CH3CH2OH+CO→CH3CH2COOH  EQ. 6Finally, as part of the interaction between the iridium catalyst and ruthenium promoter, iodine is added and removed from the iridium atoms. When the reactants are removed, the cycle is not complete and the methyl iodide results as a by-product. Methyl iodide is generated by the reaction of methanol with hydrogen iodide, which occurs at the end of the catalytic cycle. The following equation shows the formation of methyl iodide.CH3OH+HI→CH3I+H2O  EQ. 7It is important to recuperate this species, as it contains iodide that is vital to the catalytic cycle. In addition, methyl iodide is a hazardous material, so its recovery is not only advantageous, but a necessity in order to avoid hazardous emissions.
It therefore would be desirable to provide improved methods of acetic acid and glacial acetic acid syntheses, which would produces fewer unusable byproducts and which would obviate or diminish the need to use organometallic catalysts.
Fatty Acids
A variety of fatty acids are known, and some fatty acids are essential to the human body. Some of these essential fatty acids cannot be made by the body and thus must be consumed as part of the human diet. Two essential fatty acids are polyunsaturated fatty acids (PUFAs) that cannot be made in the body: linoleic acid and alpha-linolenic acid. (See FIGS. 2 and 3.) Within the body, both of these can be converted to other PUFAs, such as arachidonic acid, or omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In the body, polyunsaturated fatty acids are important for maintaining the membranes of all cells and for making prostaglandins which regulate many body processes, including inflammation and blood clotting. High levels of omega-3 fatty acids, for example, are found in oily fish, and are believed to explain the low levels of heart disease observed in populations with fish-rich diets. The fats also enable the lipid-soluble vitamins A, D, E and K to be absorbed from food, and may aid in regulating body cholesterol metabolism.
Linoleic acid is an omega-6 fatty acid. It is biologically inactive before it is catalyzed by the body into other omega-6 fatty acids gamma linoleic acid (GLA), dihomo-gamma linoleic acid (DHGLA) and arachidonic acid (AA). Linoleic acid occurs widely in plant glycerides or fats. Common sources include many vegetable oils such as flax seed, safflower, soybean, peanut, and corn, as well as dairy fats. It is essentially insoluble in water, but soluble in alcohol, ether, oils and fixed alkali hydroxides. Linoleic acid is essential in human nutrition and is used also for soaps, animal feeds, paints, drying protective coatings, emulsifying or smoothing and wetting agents, and in biochemical research. Linoleic acid appears to protect against strokes and to lower blood cholesterol, according to reports by the Journal of the American Heart Association. Other researchers report that linoleic acid may reduce the risk of ischemic stroke by lowering blood pressure and improving circulation in small blood vessels. The conjugated form of linoleic acid or CLA has been associated with health benefits such as lowered risk of cancer and atherosclerosis. Prepared CLA is available as a supplement.
Other useful fatty acids include oleic acids, as well as palmitic (C15H31COOH) and steric acids (C17H35COOH). Soybean triglycerides contain linoleic and oleic polyunsaturated fats. Fatty acids, such as these, would be useful as or useful in dietary supplements (e.g., fat burners, cholesterol reducers, biochemistry), paints, coatings, emulsifiers, pharmaceuticals, animal feed, soaps, and margarine. It would be desirable to provide new synthetic methods for making fatty acids such as linoleic and oleic polyunsaturated fats.